Conventionally, technology for configuring an electronic component includes forming a micro-electro-mechanical element such as a surface acoustic wave (SAW) resonator on a top surface of an element substrate made of piezoelectric body, enclosing the element with a metallic spacer, and then sealing the element with a sealing substrate. Examples are disclosed in Japanese Patent Application Publication No. 2008-288497 and Japanese Patent Application Publication No. 2014-143640.
FIGS. 1A and 1B show a configuration example of a conventional electronic element in which SAW resonators form a filter. FIG. 1A is a plan view showing a SAW resonator disposed on a top surface 110a of an element substrate 110, and FIG. 1B is a cross-sectional view taken along line L-L of FIG. 1A. FIG. 1A corresponds to a cross-section taken along line P-P of FIG. 1B.
The conventional electronic element 100 includes a filter circuit having wirings 140 connecting a plurality of SAW resonators 131, 132, 133, 134, 135, 136, 137 formed on the top surface 110a of the element substrate 110 made of piezoelectric body. Each of the SAW resonators 131, 132, 133, 134, 135, 136, 137 includes an interdigital transducer (IDT) electrode disposed to be sandwiched between two reflector electrodes. Further, a side wall 170 made of an electric conductor such as metal is formed on the top surface 110a of the element substrate 110 to enclose the filter circuit along the outer periphery. A bottom surface 120b of a sealing substrate 120 is supported by the side wall 170 and defines a cavity together with the top surface 110a of the element substrate 110 and the side wall 170.
Columnar signal electrodes 151, 154 and ground electrodes 155, 156, 157 are connected respectively to signal pads 141, 144 and ground pads 145, 146, 147 formed on the top surface 110a of the element substrate 110 and pass through the sealing substrate 120 from the top surface 120a to the bottom surface 120b via through-holes 120c. External signal electrode pads 181 and external ground electrode pads 185 are formed on the top surface 120a of the sealing substrate 120. Each of the signal electrodes 151, 154 and each of the ground electrodes 155, 156, 157 are connected respectively to each of the external signal electrode pads 181 and each of the external ground electrode pads 185.
FIG. 2 shows a circuit diagram of the electronic element of FIGS. 1A and 1B. The electronic element 100 includes a ladder-type filter in which the SAW resonators 131, 132, 133, 134 are arranged as series resonators and the SAW resonators 135, 136, 137 are arranged as parallel resonators.